I Special Chapters of Projective Geometry.- 1 Extensions of Projective Varieties.- 2 Proof of Theorem 1.3.- 3 Counterexamples and Further Consequences.- 4 The Zak Map of a Curve. Gaussian Maps.- 5 Quasi-homogeneous Singularities and Projective Geometry.- 6 A Characterization of Linear Subspaces.- 7 Cohomological Dimension and Connectedness Theorems.- 8 A Problem of Complete Intersection.- II Formal Functions in Algebraic Geometry.- 9 Basic Definitions and Results.- 10 Lefschetz Theory and Meromorphic Functions.- 11 Connectedness and Formal Functions.- 12 Further Results on Formal Functions.- 13 Formal Functions on Homogeneous Spaces.- 14 Quasi-lines on Projective Manifolds.- Glossary of Notation.